Silicone hydrogel contact lenses have become popular due to the ability of contact lens wearers to wear such lenses in their eyes for longer times compared to non-silicone hydrogel contact lenses. The extended time of wearing silicone hydrogel contact lenses is likely related to the high oxygen permeability (Dk) or oxygen transmissability (Dk/t) of the silicone hydrogel lens materials.
Examples of silicone hydrogel contact lenses are available from Johnson & Johnson under the tradenames Acuvue Advance and Acuvue Oasys, from Ciba Vision under the tradename Focus Night and Day, and from Bausch & Lomb under the tradename PureVision. The Acuvue Advance has the United States Adopted Name (USAN) Galyfilcon A, the Focus Night and Day lens has the USAN Lotrafilcon A, and the PureVision lens has the USAN Balafilcon A. Additional examples of suitable materials used to make silicone hydrogel contact lenses include, without limitation, senofilcon A, and lotrafilcon B.
Although existing silicone hydrogel contact lenses provide several benefits, wearing existing silicone hydrogel contact lenses can be associated with problems. For example, patients who sleep with silicone hydrogel contact lenses on their eyes are more likely to develop severe keratitis (microbial keratitis) compared to patients who don't sleep with such lenses. Other problems associated with existing silicone hydrogel contact lenses include adverse corneal responses and adverse lid responses. In addition, contact lens-induced conjunctival staining (CLICS) in regions outside of the limbus are commonly observed with silicone hydrogel contact lenses. CLICS may be observed more frequently with silicone hydrogel contact lenses that have a knife-point edge as compared to a rounded lens edge.
Silicone hydrogel contact lenses have an increased rigidity or stiffness compared to conventional hydrogel contact lenses, such as poly(2-hydroxyethyl methacrylate) (polyHEMA) containing lenses. Thus, silicone hydrogel contact lenses are less able to conform to the shape of the eye, which can result in discomfort for the patient wearing the lenses. The material properties of existing silicone hydrogel contact lenses can induce greater mechanical interaction with the cornea and conjunctival tissues compared to the non-silicone hydrogel contact lenses. The mechanical properties of silicone hydrogel contact lenses may also be associated with papillary conjunctivitis and superior epithelial splits.
Furthermore, the interaction of existing silicone hydrogel contact lenses and bulbar conjunctival tissue of a lens wearer can be significantly increased relative to non-silicone hydrogel contact lenses. This interaction can result in increased discomfort for the lens wearer and increased dilation of the blood vessels of the bulbar conjunctiva leading to an increased redness appearance of the eye of the wearer.
As discussed in U.S. Patent Publication No. 2005/0088614, corneal staining can be associated with contact lens wear. In this document, contact lenses are described which attempt to reduce peak pressure on the cornea.
Thus, there remains a need for new contact lenses, such as silicone hydrogel contact lenses, that provide improved patient comfort and that are not associated with the problems associated with existing silicone hydrogel contact lenses.